For patients with diabetes or abnormal glucose tolerance, monitoring of the blood glucose level is indispensable. A representative method among the known methods for monitoring a blood glucose level is a method using a blood sample obtained from a biological body. The method involves reacting glucose in the blood sample with an enzyme such as glucose oxidase (GOD) or glucose dehydrogenase (GDH), for example. This process generates electrons corresponding to the amount of glucose in the blood. With this known method, a voltage is applied to the blood so as to use the resultant current level for monitoring the blood glucose level.
The amount of a biological component such as blood glucose may change successively in the biological body. In order to measure the amount of change in the biological component, it has been conventionally necessary to draw blood from the subject repeatedly by needling. From the viewpoint of pain reduction and infection prevention, for example, there has been a demand for a non-invasive approach for measuring a change in the blood glucose level. Known non-invasive approaches for measuring a change in the blood glucose level include a technology for estimating the blood glucose level using the absorbance spectrum of skin, and a technology for estimating the blood glucose level using a tomographic image obtained with optical coherence tomography (OCT).